Antisolvent dewaxing of oil



Patented July 11, 1933 UNITED STATES PATENT OFFICE FREDERICK W. SULLIVAN, JR., AND CHESTER E. ADAMS, OF HAMMOND, INDIANA,

ASSIGNOBS 1'0 STANDARD OIL COMPANY, OF CHICAGO,

OF INDIANA Ho Drawing.

This invention relates to the removal of wax from oils and particularly from petroleum lubricating oils. I

The object of the invention is to provide a more efficient and a more economical means for removing wax from petroleum lubricating oils. A further object is to facilitate the preparation of oils having lower'cold tests than have heretofore been obtainable. A further object is to provide a dewaxing system wherein the war; may be removed by filtration at rapid rates. Other objects will be apparent as the description of the invention proceeds.

The invention does not extend to the broad idea of diluting an oil with naphtha, methylethyl ketone, butyl alcohol, acetone, benzene, etc., chilling and mechanically separating out the solidified wax. We have discovered that the monocarbon organic acid esters of simple alcohols, such as methyl or ethyl formates or carbonates, are particularly and unexpectedly effective as antisolvents in removing wax from oils. We have discovered that by the process hereinafter set forth we can obtain at a given chill temperature lower cold tests than can be obtained by the use of diluents heretofore used, and at the same time We can obtain satisfactory filter cakes and high filter rates.

Our invention may be applied to any wax bearing oil, but by way of illustration we will describe its application to it treated and percolated overhead lubricating oil (from mid-continent crude) having a viscosity of about 7 5 seconds Saybolt at 210 F. Such an oil contains a large amount of wax which is difficult to remove either by filtration, settling or centrifuging.

Our antisolvent is an ester of a monocarbon organic acid, such as methyl formate, ethyl for-mate, methyl carbonate, ethyl carbonate, etc. For reasons which we are unable to explain it appears that compounds of this particular character or class offer several new and unexpected advantages. They brin about a more complete removal of wax an thereby make is possible to obtain an oil of lower cold test than has been obtained with diluents heretofore used. They also cause a Application filed June 24,

ILLINOIS, A CORPORATION ANTISOLVEN T DEWAXING OF OIL 1930. Serial No. 483,567.

separation of the wax' in a physical form whichexpedites filtration.

Our antisolvents, the esters of monocarbon organic acids, arenot miscible in all proportions with oil and it'is therefore advisable to use an agent for promoting miscibility. We prefer to use benzene (benzol) for this purpose but other miscibility agents, such as toluol, maybe used.

The relative proportion of antisolvent to miscibility agent in our diluent is dependent on the particular substances used, on the.temperatures at whichthe oil is filtered, and on the ratio of diluent to oil. The number of parts by volume of antisolvent which should be present in 100 parts of diluent (antisolvent pllloils benzene) is set forth in the following ta e:

Optimum amounts of'antisolvent In dewaxing petroleum lubricating oils we prefer to dilute the oil with two and onehalf times its volume of diluent (antisolventbenzene mixture). The ratio of diluent to oil may be from 1: 1 to 4: 1, but the lower ratios give low filtration rates and the higher ratios increase dewaxing costs due to solvent losses. A ratio of 112 gives the best results, particularly when it is desired to automatically discharge the wax cake from a filter press.

The mixture of diluent and oil is rapidly chilled to a temperature of about 10 F. with or without slight agitation. A small amount of porous cellular silica (diatomaceous earth or infusorial earth), preferably about two-thirds of a pound per gallon of oil, is added to the chilled mixture to prevent any wax particles from getting through the filter cloth and to increase the rate of filtration. The mixture is then filtered through a conventional press, preferably one having cloth covered plates or leaves. The filtration may be carried out under a partial vacuum and means may be employed to circulate solvent vapors throu h a closed system to prevent loss thereof. 'fiiese features per se form no part of this invention and they will therefore not be described.

While our invention has been described in a process for separating wax from oil by filtration, it is understood that we do not limit ourselves to the details above set forth except as defined by the following claims:

We claim:

1. The method of separating viscous oil from wax which com rises diluting it with about two and one-ha f times its volume of a substantially o timum mixture of a miscibility agent an an ester of a monocarbon organic acid, chilling the diluted oil and mechanically separating the wax from the chilled oil.

2. The method of claim 1 wherein orous cellular silica is added to the cold oi prior to filtration.

3. In a method of separating oil from wax, the step which comprises diluting an oil-wax mixture with a diluent containing an ester of a inonocarbon organic acid.

4. In a method of separating oil from wax, the step which comprises diluting an oil-wax 36-72% ethyl carbonate and 64-28% benzene.

7. In a method of removing a parafiin material from oil, the ste which comprises diluting said oil with a ormate of a lower alcohol of the fatty series and an organic solvent.

8. In a method of removin a paraflin material from oil, the step-whic comprises diluting it with a mixture of a formate of a lower alcohol of the fatty series and an organic solvent, and mechanically separating the paralfin material from the diluted mixture.

9. The process of claim 7 in which the organic solvent is benzene.

10. The process of claim 8 wherein the or- 

